Process for the preparation of acrylic acid

ABSTRACT

A PROCESS FOR THE PENETRATION OF ACRYLIC ACID COMPRISING CATALYTICALLY OXIDIZING ACROLEIN IN THE VAPOR PHASE WITH MOLECULAR OXYGEN IN THE PRESENCE OF A CATALYTIC OXIDE IN WHICH THE ATOMIC RATIO OF THE CONSTITUTIONAL METAL ELEMENTS IS WITHIN THE FOLLOWING RANGE:   VAMOBWCCRDCUE   WHERE 14&lt;A$24, B=12, 4$C&lt;20, 1 $D&lt;10 AND   0$E&lt;12

United States Patent US. Cl- 260-530 N 4 Claims ABSTRACT OF THE DISCLOSURE A process for the preparation of acrylic acid comprising catalytically oxidizing acrolein in the vapor phase with molecular oxygen in the presence of a catalytic oxide in which the atomic ratio of the constitutional metal elements is within the following range:

V,,Mo ,W Cr Cu where 14 a24, b=12, 4c 20, 1d 10 and This invention relates to a process for the preparation of acrylic acid by the catalytic vapor phase oxidation of acrolein.

In industrial processes of the catalylic vapor phase oxidation of unsaturated aldehydes to obtain the corresponding unsaturated carboxylic acids, it is generally very important to employ catalysts capable of giving high conversion of the starting unsaturated aldehydes and high selectivities for the intended unsaturated carboxylic acids. Further, it is also required that these catalysts can be prepared simply and easily and that they exhibit a high activity of excellent stability during long time use.

Molybdenum oxide-vanadium oxide series catalysts have heretofore been known as catalysts for use in the preparation of acrylic acid by the catalytic vapor phase oxidation of acrolein. Among the catalysts of this type, those comprising a major amount of vanadium oxide tend to allow the oxidation to proceed completely. Therefore, when such catalysts are used for the oxidation of acrolein, the amounts of carbon dioxide gas and water formed increase and the selectivity to acrylic acid is considerably lowered. For this reason, each of the industrially applicable catalysts of this type comprises a major amount of molybdenum oxide. For instance, the specification of Japanese patent application publication No. 1,775 66 discloses that a catalyst in which the Weight ratio of molybdenum oxidezvanadium oxide is within the range of from 2:1 to 8:1 is effective for preparing acrylic acid from acrolein. Also US. Pat. No. 3,567,773 teaches that a catalyst comprising 1-6 vanadium atoms per 12 molybdenum atoms is effective for the preparation of acrylic acid by the oxidation of acrolein.

An object of this invention is to provide a process for the catalytic vapor phase oxidation of acrolein which can be practised industrially advantageously by developing a novel catalyst which can be conveniently used in the high space velocity reaction and can give acrylic acid of high purity in high yield.

Other objects of this invention will be apparent from the description given hereinbelow.

As a result of research it has now been found that a catalytic oxide comprising as constitutional elements vanadium, molybdenum, tungsten and chromium (and copper) in which the amount of vanadium is, contrary to known catalysts, greater than the amount of molybdenum, can attain the above-mentioned object of this invention.

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The catalytic oxide of this invention is characterized in that the metal constituents of the oxide are present at the following specific atomic ratio:

It is unnecessary for oxygen to be present in the special reduced state in the catalytic oxide. It is assumed that the oxygen is present in the catalytic oxide in the form of a complicated metal oxide or metallic acid salt. Therefore, the amount of oxygen contained in the catalytic oxide varies depending on the atomic ratio of the metal elements constituting the catalytic oxide.

In thi invention, the catalytic oxide may be used for the reaction in the form supported on a suitable inactive carrier, if necessary. As such inactive carrier inactive porous substances in either naturally occurring forms may be employed or preformed granular forms. Examples of such inactive porous substances are alpha-alumina, silicon carbide, pumice, silica, zirconia, magnesium silicate, titanium oxide and mixtures thereof. In this invention, it is desirable to employ an inactive porous carrier having a specific surface area of less than 2 m. /g. and a porosity of 10- 65% in which at least of pores have a macropore diameter of 20 to 1500 microns.

The catalyst to be used in this invention may be prepared, for instance, by adding an aqueous solution of ammonium dichromate (and an aqueous solution of copper nitrate) to an aqueous solution containing ammonium molybdate, ammonium paratungstate and ammonium metavanadate, throwing a desired carrier into the resulting aqueous mixture, heating and evaporating the mixture to dryness to deposit the above metal compounds on the carrier, otherwise molding the solid into a desired form, for instance, into tablets, if necessary, and thereafter calcining the same at a temperature of 350 to 600 C. Of course, the use of the carrier may be omitted in the above method. Further, not only the above-mentioned ammonium salts and nitrates but also compounds capable of being formed into the intended catalytic oxide under calcination conditions, such as hydroxides and carbonates, may be used as starting compounds for the preparation of the catalyst in this invention.

The catalytic vapor phase oxidation process according to this invention can be accomplished by introducing a gaseous mixture comprising 110% by volume of acrolein, 315% by volume of molecular oxygen and 10-60% by volume of steam, the balance being gases not substantially pertaining to the reaction, onto a catalyst prepared in such manner as described above, at a temperature of 200 to 350 C. under a pressure ranging from atmospheric pressure to 10 atmospheres. During the oxidation, the space velocity is maintained at a level of 2000 to 8000 hrrl. The reaction may be carried out either in a fixed bed or in a fluidized bed.

A gas obtained by the catalytical vapor phase oxidation of propylene in the presence of a catalyst, or a gas formed by replenishing air or oxygen in such gas from the oxidation of propylene may be used as the above-mentioned gaseous mixture. The above product gas from the oxidation of propylene usually comprises acrylic acid, unreacted propylene, propane, acetaldehyde, acetic acid and the like in addition to oxygen, nitrogen, steam and acrolein. As is illustrated in Example 9 given hereinbelow, however, such product gas may be used in this invention without any disadvantage.

As is shown in the examples given hereinbelow, in this invention the catalyst activity can be maintained stable at a high level for a long period of time and the one- 3 4 pass yield of acrylic acid can be maintained at a high space velocity of the gaseous mixture was maintained at level without reduction of the space velocity. 3600 hlf Although not wishing to be limited by theoretical prin- Results of the reaction are shown in Table 1. When the ciples, it is assumed that the reason for the above menreaction was continued for 720 hours (one month) under tioned effects is probably due to the fact that complicated 5 the same reaction conditions, the one-pass yield was mainoxides or acid salts of tungsten and chromium (and tained at a high level, i.e. 90.5%. copper) are combined with those of V-Mo series to there- COMPARATIVE EXAMPLE 1 by adjust the catalyst efficiency and that when a carrier is used, the catalyst efficiency is further controlled by the A Catalyst conslstmg of p acarrier it f th carrien supported thereon, a catalytic oxide having the metal This invention will now be explained more specifically elemfint composltlon, 12 25 Was P p y by reference to examples and comparative examples. Peeling the Procedure 0f Example 1 WithQut employing The conversion, selectivity and one-pass yield used in amonium Paramngstate and ammounium dlclll'omatethe insta t specification are as d fi d b l The oxidation of acrolein was carried out under the same conditions as in Example 1 with use of the so pre- Converslon (percent) 15 pared catalyst. Results are shown in Table 1.

X100 COMPARATIVE EXAMPLE 2 number of moles of fed acrolein A l f 1 h 1 d cata yst consisting 0 an a p a-a umina carrier an selectwlty (percent) supported thereon, a catalytic oxide having the metal elenumber of moles of formed acrylic acid ment composition, VIEMOIZWGBCISZ was prepared by number of moles reacted acrolein repeating the procedure of Example 1 Without employing O yield t) ammonium dichromate.

The oxidation of acrolein was carried out under the x100 clonditions as in Example 1. Results are shown in EXAMPLE 1 COMPARATIVE EXAMPLE 3 While 5000 ml. of water were being heated with stir- A catalyst was prepared by repeating the procedure of ring, successively 293 g. of ammonium paratungstate, 280 Example 1 without employing ammonium paratungstate,

number of moles of reacted acrolein number of moles of formed acrylic acid number of moles of fed acrolein g. of ammonium metavandate, 338 g. of ammonium ammonium dichromate and copper nitrate. molybdate and g. of ammonium dichromate were The reaction was carried out under the same conditions added into water. Separately, 200 g. of copper nitrate as in Example 1 with use of the so prepared catalyst. were dissolved in 500 ml. of water. Both aqueous solutions Results are shown in Table 1.

TABLE 1 One-pass Selectivity yield of Catalyst composition (atomic ratio) Reaction Space Acrolein to acrylic acrylic temperature velocity conversion acid acid V Mo W 01' 11 C. (hrr (percent) (percent) (percent) Example1 15 12 6.8 2 0 5.2 265 3,500 97.0 93.0 90.2 Comparative Exampl 1 e 15 12 0 0 5.2 265 3,600 61.0 75.2 45.9 15 12 6. 5 0 5. 2 265 a, 600 47. 0 82. 1 38. 5 15 12 o 0 0 265 3,600 58. 0 53. 0 30. s

were mixed. The aqueous mixture and 1000 ml. of EXAMPLES 2-7 granular alpha-alumina having a diameter of 3-5 mm. which had a specific surface area of less than 1 m. /g. and Example 1 was repeated by varying the atomic ratio a porosity of 25% and in which 92% of the pores had of the metal elements in the catalytic oxide and the reaca macropore diameter of 30-250 microns were put into tion conditions as indicated in Table 2. Results are a porcelain evaporating dish, and they were evaporated shown in Table 2.

TABLE 2 One-pass Selectivity yield of Catalyst composition (atomic ratio) Reaction Space Acrolein to acrylic acrylic temperature velocity conversion acid acid V Mo W Cr Cu C.) (hrr (percent) (percent) (percent) 16 12 6. 8 2. 0 5. 2 {265 3,600 97. a 92. 5 90. 0 280 5,000 95. 0 94. 1 s9. 4 16 12 8.0 3. 0 5. 2 280 3,600 94. 0 94. 0 88. 4 1s 12 6. s 2. 0 7. 0 245 3, 600 97. 5 92. 0 s9. 7 18 12 5. 0 4.0 5. 2 {250 3,600 96. 0 90. 0 86. 4 275 5, 000 94. a 93. 7 88. 8 20 12 6. 8 7. 0 5. 2 275 3, 600 96. 5 90. 5 s7. 4 1s 12 6. s 2. 0 0 285 3,600 96. 5 90. 5 e7. 4

to dryness on a hot water bath. The resulting solid was EXAMPLE 8 calcined at 400 C. for 5 hours.

As a result a catalyst consisting of an alpha-alumina The reaction was carried out under the same conditions carrier and, supported thereon, a catalytic oxide of the as in Example 1 except that silicon carbide of a diameter metal composition, V Mo W cr Cu wa obtained. of 3-5 mm. which had a surface area of less than 1 m. g.

The so prepared catalyst (1000 ml.) was packed in a 7 and a P y of 21% and in which 95% of pores had a U-shaped stainless steel tube having a diameter of 25 macropor diameter of 30-500 microns was used as the mm., and the tube was immersed in a molten nitrate bath a rheated at 265 C. A gaseous mixture comprising 6% by As a result, acrylic acid was formed at an acrolein convolume of acrolein, 54% by volume of air and 40% by version of 97.2%, a selectivity to acrylic acid of 92.8%

volume of steam was introduced into the tube, and the and an acrylic acid one-pass yield of 90.2%.

EXAMPLE 9 Acrolein 5.01 Propylene plus propane 7 0.58 Acrylic acid plus acetic acid 0.60 Nitrogen 51.0 Oxygen 6.50 Steam 34.0 Others 2.31

When the calculation was conducted based on the assumption that propylene, propane, acrylic acid, acetic acid and the like in the above gaseous mixture were not reacted, acrylic acid was formed by the above reaction at an acrolein conversion of 97.5%, a selectivity to acrylic acid of 92.8% and an acrylic acid one-pass yield of 90.5%.

What we claim is:

1. A process for the preparation of acrylic acid comprising catalytically oxidizing in the vapor phase acrolein with molecular oxygen in the presence of a catalytic oxide consisting essentially of the following metal elements within the atomic ratio range of:

2. A process for the preparation of acrylic acid comprising catalytically oxidizing in the vapor phase-acrolein with molecular oxygen at a temperature of 200 to 350 C. under a pressure ranging from atmospheric pressure to 10 atmospheres at a space velocity of 2,000 to 8,000 hr. in the presence of a catalytic oxide consisting essentially of the following metal elements within the atomic ratio range of:

V Mo W Cr Cu 3. A process for the preparation of acrylic acid comprising catalytically oxidizing in the vapor phase acrolein with molecular oxygen in the presence of a catalyst consisting essentially of inactive carrier and, supported thereon, a catalytic oxide consisting essentially of the following metal elements within the atomic ratio range of:

V Mo W Cr Cu said inactive carrier having a specific surface area of less than 2 m. g. and a porosity of 10-65% and at least of pores of the carrier having a macropore diameter of 20 to 1,5000 microns.

4. A process for the preparation of acrylic acid comprising catalytically oxidizing in the vapor phase acrolein with molecular oxygen at a temperature of 200 to 350 C. under a pressure ranging from atomspheric pressure to 10 atmospheres at a space velocity of 2,000 to 8,000 hr.- in the presence of a catalyst consisting essentially of an inactive carrier and, supported thereon, a catalytic oxide consisting essentially of the following metal elements Within the atomic ratio range of:

V Mo W Cr Cu wherein 14 a 24, b=12, 4c 20, 1d l0 and 0e 12. said inactive carrier having a specific surface area of less than 2 mF/g. and a porosity of 10-65% and at least 90% of pores of the carrier having a macropore diameter of 20 to 1,500 microns.

References Cited FOREIGN PATENTS 1d 10 and 1,084,143 9/1967 Great Britain 260-530 N 1,086,523 10/1967 Great Britain 260-530 N 746,202 8/1970 Belgium 260530 N JAMES A. PATTEN, Primary Examiner R. D. KELLY, Assistant Examiner U.S. Cl. X.R.

UMTED STATES PATENT OFFICE CER'NFICATE UP CURREC'HQN Pat nt No. 397759474 Dated November 27, 1973 Takashi OHARA AL Inventor(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 6, line 15: cancel "1,5000" and substitute therefor Column 4, line 10: cancel "V M0 Cu and substitute therefor --V 5MO12CU5 2 Column 4, line 12: cancel "amonium" and "ammounium" and substitute therefor in both instances "ammonium-- Signed and sealed this 9th day of April 197L (SEAL) Attest:

EDWARD MELETGHLR, JR. C Q MARSHALL DANN Commissioner of Patents Attesting Officer.

FORM 1 0-1050 (10-69) USCOMM DC 6376 p6'9 u.s. covzmmsm PRINTING OFFICE 1969 osss-su 

